Welding gases are used with laser welding and surface treatment. Welding gases protect the smelt and the surface of the heated material against reaction with the surrounding air.
Checking the formation of plasma is an important factor regarding laser welding with carbon dioxide laser and high outputs. Typical gases used in laser welding with carbon dioxide laser are helium and helium/argon mixtures. Helium suppresses the formation of plasma and is therefore often used in connection with higher laser outputs. Argon generates a large amount of plasma and should therefore not be used in connection with high laser outputs. For certain applications mixtures of argon with oxygen, carbon dioxide and other additives may be used. An alternative to helium regarding laser welding is LASGON®, a specially developed program with tailor-made gas mixtures for different laser welding applications.
Argon/hydrogen mixtures give high productivity and weld quality in the welding of austenitic stainless steel. With regard to, for example, ferritic stainless steel, hydrogen mixtures should not be used.
When laser welding with Nd:YAG laser, argon is recommended as the welding gas. Helium is rarely used as the welding gas as the plasma formation is not as critical as in Nd:YAG laser welding with normal laser outputs. From a quality perspective argon often provides a better result than helium.
Gases for surface treatment with laser
In principle, the same gases are used as with laser welding. Noble gases, i.e. argon and helium, provide protection against the effect of the atmosphere on the heated material’s surface. In certain cases nitrogen may be used, depending on which type of material is being worked on and which additive material is employed. Argon/nitrogen mixtures are also used for certain applications.
Beam gas
The beam between the laser and the cutting/welding head consists of mirrors and other sensitive equipment. Pollution in the beam can have a negatively effect on the actual laser beam. In addition, the mirrors may become covered in pollution. This causes increased wear while reducing beam quality. Pollution by argon, oxygen, humidity and hydrocarbons should be avoided while minimizing particle content. One solution is to use a beam gas, a pure particle-free gas supplied in the beam. Laser Nitrogen or Laser Nitrogen Ultra is normally used as the beam gas. Consumption often lies at around 1-3 m³/hour.